Patent Literature 1 discloses a device for detecting capacitance values of respective electrostatic capacitors which are distributed in a matrix manner, that is, a capacitance detecting device for detecting distribution of capacitance values of respective electrostatic capacitors which are defined by M drive lines and L sense lines so as to be arranged in a matrix manner. When a touch panel is touched with a finger or a pen, the capacitance detecting device detects the touch of the finger or pen by detecting a change in capacitance value of an electrostatic capacitor that corresponds to a part of a touch panel, which part is touched by the finger or the pen.
FIG. 23 is a view schematically illustrating a configuration of a conventional touch panel system 91. FIG. 24 is an explanatory view for describing a method of driving the touch panel system 91. The touch panel system 91 includes a touch panel 92. The touch panel 92 includes drive lines DL1 through DL4, sense lines SL1 through SL4, and electrostatic capacitors C11 through C44 which are provided at respective intersections where the drive lines DL1 through DL4 and the sense lines SL1 through SL4 intersect with each other.
The touch panel system 91 includes a driving section 94. The driving section 94 drives the drive lines DL1 through DL4 on the basis of a code sequence of four rows and four columns which is represented by Expression 3 in FIG. 24. The driving section 94 applies a voltage Vdrive in a case where an element of the code sequence equals to “1”, whereas the drive section applies no voltage in a case where the element equals to “0”.
The touch panel system 91 includes four amplifiers 98 which are provided for the respective sense lines SL1 through SL4. Each of the amplifiers 98 receives and amplifies linear sums Y1, Y2, Y3, and Y4 of electrostatic capacitors, which are provided along a sense line to which the amplifier 98 is connected among the sense lines SL1 through SL4, and are driven by the driving section 94.
For example, in the first driving of four drivings based on the code sequence of four rows and four columns, the driving section 94 applies a voltage Vdrive to the drive line DL1, while applying no voltage to the drive lines DL2 through DL4. For example, from the amplifier 98 connected to the sense line SL3, a measurement value Y1 (see Expression 1 in FIG. 24) of the electrostatic capacitor C31 is outputted as a result of the application of the voltage Vdrive.
In the second driving of the four drivings, the driving section 94 applies a voltage Vdrive to the drive line DL2, while applying no voltage to the drive lines DL1, DL3, and DL4. In this case, a measurement value Y2 (see Expression 2 in FIG. 24) of the electrostatic capacitor C32 is consequently outputted from the amplifier 98 connected to the sense line SL3.
In the third driving of the four drivings, the driving section 94 applies a voltage Vdrive to the drive line DL3, while applying no voltage to the drive lines DL1, DL2, and DL4. In the fourth driving of the four drivings, the driving section 94 applies a voltage Vdrive to the drive line DL4, while applying no voltage to the drive lines DL1, DL2, and DL3.
The measurement values Y1, Y2, Y3, and Y4 are correlated with respective electrostatic capacitance values C1, C2, C3, and C4 (see Expressions 3 and 4 in FIG. 24). Note that, for simple description, a coefficient (−Vdrive/Cint) for each of the measurement values Y1 through Y4 is omitted from Expressions 3 and 4 in FIG. 24.